The invention relates generally to electromagnetic radiation reflectors. In particular, the invention relates to signal reflectors to redirect and/or reshape electromagnetic radiation.
Radiation reflectors include reflect-arrays, which are known to those skilled in the art of antenna designs as useful for reflecting an electromagnetic wave at various angles by controlling the phase of the elements that compose the array.
A phased array can be used to control electromagnetic radiation. By controlling the phase of each element within the array, a narrow electromagnetic beam can be formed. By dynamically changing the phase in a way known to those skilled in the art of antenna design, the beam can be steered, as reported by A. J. Fenn et al., “The Development of Phased-Array Radar Technology”, LINCOLN Laboratory Journal, 12 321-340 (2000), available at https://www.ll.mitedu/publications/journal/pdf/vol12_no2/12_2devphasedarray.pdf.
Reflect-arrays are similar to phased arrays but the elements in the array produce no radiation of their own. Instead, each element is a reflector that reflects a small portion of incident radiation. Often, the elements are designed to be resonant at a given frequency or over a range of frequencies. By controlling the resonance, the phase of the reflected signal can be dynamically controlled into different directions as reported by D. G. Berry et al., “The Reflectarray Antenna”, IEEE Transactions on Antennas and Propagation, 11 645-651 (1963).
The transition between two phases in a reflect-array often occurs over a very narrow range of control parameters. Precise control of the phase of each element can be difficult in relation to the others in order to achieve precise beam steering. Further, due to material losses and resonant component losses, the amplitude of the reflected signal can be dramatically reduced at resonance, which is often an undesirable effect.